Hey 8.1l owners I am new to truck forum and trying to find someone who has possibly done this. I have a 2002 2500hd silverado 4x4 with 8.1l. I love the truck and bought it thinking I was going to a larger fith wheel but am going with a motorhome instead. I love the truck so intend on keeping it. I am running 4.10 gears which is great neck snapping fun but highway trips over 60 mph kill any sort of mileage. Best i ever got going across the nevada flat straight desert with a tail wind empty was 13.8. Has anyone ever had this set up and swapped to 3.73 with any success. I dont need the massive low end torque since I dont pull heavy and am thinkin the lower rpm on the open road should give me a couple mpgs better. I penciled it out at $3.50 per gallon at a cost of swapping it being around 2000.00 dollars It would pay for it self in 37000 miles if I can get a 3mpg increase. Oh ya it has the allison and everything including tires is bone stock at 76000 miles.